There are more than ten thousand species of pests that cause losses in agriculture. The world-wide agricultural losses amount to billions of U.S. dollars each year. Stored food pests eat and adulterate stored food. The world-wide stored food losses amount to billions of U.S. dollars each year, but more importantly, deprive people of needed food. Certain pests have developed resistance to pesticides in current use. Hundreds of pest species are resistant to one or more pesticides. The development of resistance to some of the older pesticides, such as DDT, the carbamates, and the organophosphates, is well known. But resistance has even developed to some of the newer pesticides. As a result, there is an acute need for new pesticides that has led to the development of new pesticides. Specifically, US 20130288893(A1) describes, inter alia, certain pesticidal thioethers and their use as pesticides. Such compounds are finding use in agriculture for the control of pests.
In U.S. Pat. No. 9,102,655, processes for preparing such pesticidal thioethers were described. In one embodiment, the intermediate 1c, described therein, was prepared by contacting a compound of the formula 1b, described therein, with 3-bromopyridine or 3-iodopyridine in the presence of a copper salt, an inorganic base and N,N′-dimethylethane-1,2-diamine (DMEDA) as shown in the exemplary Scheme 1 below.

The process, known as an Ullmann coupling, is carried out in the presence of DMEDA to serve as a ligand for the copper salt. Because DMEDA is a costly material (roughly $256/kg) and is used in amounts between about 0.4 and 0.6 molar equivalents compared to compound 1b, manufacture of the target pesticidal thioethers described in U.S. Pat. No. 9,102,655 and US Patent Publication 20130288893(A1) is more expensive.
Because there is a need for very large quantities of pesticides, particularly pesticidal thioethers of the type described in U.S. Pat. No. 9,102,655 and US Patent Publication 20130288893(A1), it would be highly advantageous to develop new processes to produce pesticidal thioethers efficiently and in high yield from economical commercially available starting materials.